Marta and Montgomery, a brother and a sister, find, one day on the beach, an ectoplasmic creature which they recognize to be a sea monster. He is a large, likable creature with a substantial appetite, but Marta and Montgomery are perplexed as to exactly what it is he likes to eat. When it becomes evident--from observing his behavior with certain natives--that the monster is particularly fond of snacking on human beings, they wisely ship him off to New York City where he will have a plentiful supply of nutritious tidbits.